20 THE TABLES: EXPLANATORY 



then look up the vital capacity corresponding to these 

 measurements. In this way information will be gained 

 that will subsequently be of service in determining the 

 significance of future changes in weight, vital capacity, 

 and percentage deviation from the normal. Where an 

 individual has lost considerably in weight it must be 

 borne in mind that the chest-measurement will also have 

 become slightly less. Hence the figures derived from this 

 measurement will often show a smaller deficiency than 

 those obtained from the trunk-length, which naturally 

 shows no such change. Again, however, the advantage 

 from averaging both sets of figures balances the rela- 

 tively small errors introduced by the change in one of 

 the measurements. The knowledge to which class an 

 individual is likely to belong is also of particular im- 

 portance when changes in vital capacity are studied in 

 connection with various diseases. 



It is perhaps worth recording that changes in the vital 

 capacity appear to offer an unusually trustworthy index 

 of any improvement or deterioration taking place in the 

 pulmonary lesions of patients with tuberculosis of the 

 lungs. It also appears from the study of a tolerably large 

 number of such cases that determinations of the vital 

 capacity and its changes may be of value in prognosis, 

 and help the physician to decide, for example, which 

 patients are likely to benefit by further sanatorium 

 treatment and which are not. (See "The Vital Capacity 

 Constants Applied to Pulmonary Tuberculosis," by 

 Georges Dreyer and L. S. T. Burrell, Lancet, June 5, 

 1920, cxcviii, 1212.) 



